The structures of diverse toxic alkaloids from frogs of the genera Dendrobates, Colosthetus and Atelopus have been isolated. The pharmacological activity of batrachotoxin and histrionicotoxin analogs have been studied in detail. Radioactive batrachotoxin, tetrodotoxin and histrionicotoxin have been prepared and are being used to study their ultrastructural site of action. The synthesis of dodecahydrohistrionicotoxin is in progress.